Directional cell migration, chemotaxis, underlies leukocyte infiltration, recruitment, trafficking and homing, which are not only required for normal immune responses, but also responsible for many inflammation-related diseases including ischemic reperfusion, atherosclerosis, asthma, and sepsis. In addition, cell migration occurs in embryonic development, wound healing, and tumor metastasis. Our long term goal is to understand the signaling mechanisms by which chemoattractants regulate leukocyte chemotaxis and their roles in inflammation-related diseases models with the mouse primary neutrophil as the model cell. The central hypothesis of this study is that multiple signaling pathways may function together to regulate neutrophil polarization and directionality. The goals of this application are to fully characterize two new signaling mechanisms and elucidate how these signaling pathways regulate neutrophil chemotaxis in vitro and recruitment in vivo. We will use a combination of molecular and cell biological, biochemical, transgenic, proteomic, functional genomic and advanced in vitro and in vivo imaging approaches to accomplish the following specific aims: 1) To elucidate the novel signaling mechanisms by which cofilin phosphorylation, an event underlining actin remodeling, is regulated by chemoattractants via PLC and PI3K in neutrophils and the role of the signaling mechanism in regulating neutrophil polarization and directionality. 2) To investigate the mechanisms by which integrin signaling regulates PIP5K1C polarization, that has important roles in regulating neutrophil chemotaxis and interaction with endothelial cells. 3) To investigate the roles of these chemoattractant signaling pathways and their interactions in neutrophil chemotaxis in vitro and recruitment in vivo.